1. Field of the Invention
This invention relates generally to read/write head arrays for magnetic data stores and more particularly to a read/write shield-pairing technique for optimizing head surface wear.
2. Description of the Prior Art
Business, science and entertainment applications depend upon computers to process and record data, often with large volumes of the data being stored or transferred to nonvolatile storage media, such as magnetic discs, magnetic tape cartridges, optical disk cartridges, floppy diskettes, or floptical diskettes. Typically, magnetic tape is the most economical means of storing or archiving the data. Storage technology is continually pushed to increase storage capacity and storage reliability. Improvement in data storage densities in magnetic storage media, for example, has resulted from improved medium materials, improved error correction techniques and decreased areal bit sizes. The data capacity of half-inch magnetic tape, for example, is now measured in tens of gigabytes on 256 data tracks.
The improvement in magnetic medium data storage capacity arises in large part from improvements in the magnetic head assembly used for reading and writing data on the magnetic storage medium. A major improvement in transducer technology arrived with the magnetoresistive (MR) sensor originally developed by the IBM corporation. The MR sensor transduces magnetic field changes in a MR stripe to resistance changes, which are processed to provide digital signals. Data storage density can be increased because a MR sensor offers signal levels higher than those available from conventional inductive read heads for a given bit area. Moreover, the MR sensor output signal depends only on the instantaneous magnetic field intensity in the storage medium and is independent of the magnetic field time-rate-of-change arising from relative sensor/medium velocity.
The quantity of data stored on a magnetic tape may be increased by increasing the number of data tracks on the tape, which also decreases the distance between adjacent tracks and forces adjacent read/write heads closer together. More tracks are made possible by reducing feature sizes of the read and write elements, such as by using thin-film fabrication techniques and MR sensors. In operation the magnetic storage medium, such as tape or a magnetic disk surface, is passed over the magnetic read/write (R/W) head assembly for reading data therefrom and writing data thereto. In moderm magnetic tape recorders adapted for computer data storage, read-while-write capability with MR sensors is an essential feature for providing fully recoverable magnetically stored data. The interleaved R/W magnetic tape head with MR sensors allows increased track density on the tape medium while providing bi-directional read-while-write operation of the tape medium to give immediate read back verification of data just written onto the tape medium. A read-while-write head assembly includes, for each of one or more data tracks, a write element in-line with a read element, herein denominated a AR/W trackpair,@ wherein the gap of the read element is closely-disposed to and aligned with the gap of the write element, with the read element positioned downstream of the write element in the direction of medium motion. By continually reading Ajust recorded@ data, the quality of the recorded data is immediately verified while the original data is still available in temporary storage in the recording system. The recovered data is compared to the original data to afford opportunity for action, such as re-recording, to correct errors. In the interleaved head, the R/W track-pairs are interleaved to form two-rows of alternating read and write elements. Alternate columns (track-pairs) are thereby disposed to read-after-write in alternate directions of tape medium motion. Tape heads suitable for reading and writing on high-density tapes also require precise alignment of the track-pair elements in the head assembly.
Tape heads in particular suffer from head wear caused by motion of the magnetic recording tape. Repeated passes of the tape medium over the wear-resistant tape head surface may eventually wear away some of the surface, which can impair head performance. This may be a particular problem for thin-film magnetic heads where the thin-film layer structure may see relatively considerable wear with brief operation, giving an unacceptably short lifetime for the magnetic head assembly. Practitioners in the art provide very hard wear-resistant layers on the air bearing surfaces of magnetic heads to inhibit wear, for example, a sputtered layer of diamond-like carbon or titanium-carbide, but such layers are also very thin, being perhaps 20 nanometers thick.
While wear mechanisms are not perfectly understood in the art, one problem is believed to arise from accelerated wear in line with the write gap, which is disadvantageous for head-assembly life-expectancy. The wear difference is media-dependent and can be severe enough to make certain media incompatible with such head assemblies.
There is accordingly a clearly-felt need in the art for a wear-resistant interleaved read/write head assembly with improved symmetric wear characteristics. These unresolved problems and deficiencies are clearly felt in the art and are solved by this invention in the manner described below.
The purpose of this invention is to optimize head wear by equalizing the voltage environments of the read and write heads to reduce electrochemical/mechanical erosion of the wear-resistant air bearing surface (ABS) layer. This is accomplished by adding an electrical connection between adjacent electrically conductive reader shields and writer poles/shields. For thin-film multi-track read/write arrays, such connection is provided independently for each pair of read/write elements in the array.
It is a feature of this invention that a write-gap pole is provided adjacent the read gap shield. It is another feature of this invention that at least one and preferably both read gap shields is electrically-clamped to one of the MR signal leads (preferably the lead having the most positive potential) or to both MR leads via a center-tapped resister clamping structure that may be appreciated with reference to the commonly-assigned U.S. Pat. No. 6,246,553 incorporated herein by reference.
It is an advantage of this invention that a write-gap pole or shield of the type used by IBM Corporation for head manufacturability can be easily connected by a conductor to the adjacent read-gap shield.
In one aspect, the invention is a magnetic head assembly including a write gap formed between two spaced magnetic pole tips and a magnetoresistive (MR) sensor element having opposite ends each connected to a respective electrical lead conductor, the MR sensor element and the two electrical lead conductors being disposed in spaced relationship between two MR element shields, wherein the improvement includes a first electrical conductor coupling at least one of the MR element shields and at least one of the electrical lead conductors and a second electrical conductor coupling the one MR element shield and one of the write-gap poles.
In another aspect, the invention is a magnetic head assembly having an air bearing surface (ABS), including a read head having a magnetoresistive (MR) sensor element with opposite ends each connected to a respective electrical lead conductor, the MR sensor element and the two electrical lead conductors being disposed in spaced relationship between two MR element shields and a first electrical conductor coupling at least one of the MR element shields and at least one of the electrical lead conductors; a write head having two magnetic pole pieces each with a pole tip portion disposed adjacent the ABS and a write gap located between the pole tip portions; and a second electrical conductor coupling the one MR element shield and one of the write-gap poles.
In yet another aspect, the invention is a magnetic tape drive with at least one magnetic head assembly that has an air bearing surface (ABS), the tape drive including a magnetic recording medium having a recording surface, a motor for moving the magnetic recording medium, and a head-mount assembly for supporting the magnetic head assembly with respect to the magnetic recording medium; where the read head includes a magnetoresistive (MR) sensor element having opposite ends each connected to a respective electrical lead conductor, the MR sensor element and the two electrical lead conductors being disposed in spaced relationship between two MR element shields and a first electrical conductor coupling at least one of the MR element shields and at least one of the electrical lead conductors; where the write head includes two magnetic pole pieces each having a pole tip portion disposed adjacent the ABS and a nonmagnetic write gap located between the pole tip portions; and a second electrical conductor coupling the one MR element shield and one of the write-gap poles.
In a further aspect, the invention is a method for making a magnetic head assembly that has an air bearing surface (ABS), including the unordered steps of (a) making a read head with the steps of forming a magnetoresistive (MR) sensor element having two ends disposed adjacent the ABS in spaced relationship between two MR element shields, forming an electrical lead conductor coupled to each MR sensor element end, and forming a first electrical conductor coupling at least one of the MR element shields and at least one of the electrical lead conductors, (b) making a write head with the steps of forming two magnetic pole pieces each having a pole tip portion disposed adjacent the ABS and forming a nonmagnetic write gap located between the pole tip portions, and (c) forming a second electrical conductor coupling the one MR element shield and one of the write-gap poles.